The present invention relates to a method of supplying ready-to-use dialysis fluid in a machine for extracorporeal blood treatment, and it concerns a machine for extracorporeal blood treatment with a device for supplying ready-to-use dialysis fluid.
Dialysis fluid is usually prepared online from fresh water and an electrolyte concentrate, the latter being inherently sterile and freshwater usually being free of microorganisms. However, there is no guarantee that dialysis fluid prepared in this way will be absolutely sterile. German Patent No. 3,641,843 describes a hemodialysis machine in which the dialysis fluid circuit has a sterile filter upstream from the dialysis fluid chamber to supply an absolutely sterile dialysis fluid to the dialyzer.
In hemodiafiltration, dialysis fluid can be prepared online from fresh water and an electrolyte concentrate, and the replacement fluid can be prepared online from the dialysis fluid. Although the electrolyte concentrate is usually sterile, and fresh water does not usually contain any microorganisms, this does not guarantee that the dialysis fluid prepared online will be absolutely sterile and pyrogen-free, which is why dialysis fluid for preparing the replacement fluid is converted to an absolutely sterile and pyrogen-free condition. This is done by preparing dialysis fluid upstream from the dialyzer and passing it through at least one filter which is divided into two chambers by a hydrophilic membrane that retains microorganisms. Such a device with two sterile filters arranged in the dialysis fluid system is known from German Patent No. 3,444,671 A and European Patent No. 692,268 A, for example.
To prevent microbes or pyrogens from clogging the sterile filters, it is known that the membrane of the sterile filter may occasionally be rinsed off with dialysis fluid.
European Patent No. 694,312 A describes a hemodiafiltration machine with a sterile filter arranged in the dialysis fluid path, where its membrane can be rinsed off with dialysis fluid through a line. A bypass line connects the dialysis fluid inlet line leading to the dialyzer to the dialysis fluid outlet line leading to the drain.
With the known blood treatment equipment with sterile filters in the dialysis fluid path, there is the risk that dialysis fluid at the wrong temperature or conductivity might reach the dialyzer.
Although the first chamber of the sterile filter is flushed with dialysis fluid, for example, fluid dwells in the second chamber of the filter when the treatment is interrupted. Then after the treatment is continued, the fully cooled fluid is sent to the dialyzer. Dialysis fluid at an excessively high temperature can reach the dialyzer when there is a disturbance in the temperature control of the device for supplying dialysis fluid.
The object of the present invention is to provide a method of supplying ready-to-use dialysis fluid in a machine for extracorporeal blood treatment, which increases the safety of the blood treatment inasmuch as dialysis fluid reaches the dialyzer at a predetermined temperature or conductivity even after passing through the sterile filter. This object is achieved according to the present invention as described and claimed herein.
Another object of the present invention is to create a machine for the extracorporeal blood treatment so that its safety is increased inasmuch as dialysis fluid reaches the dialyzer at a predetermined temperature or conductivity even after passing through the sterile filter. This object is achieved according to the present invention as described and claimed herein.
With the method and device according to the present invention, the second bypass valve is opened after the first bypass valve is closed, thus interrupting the rinsing operation in the first chamber of the sterile filter, so that fluid present in the second chamber of the filter at a temperature and/or conductivity not conforming to a preset level is discharged through the second bypass line into the outlet. This prevents dialysis fluid at the wrong temperature and/or with the wrong composition from reaching the dialyzer.
The temperature and/or conductivity of the dialysis fluid is monitored while the dialysis fluid is flowing to the outlet, bypassing the dialyzer. If the deviation in the measured conductivity and/or temperature from a predetermined conductivity and/or temperature value is below a certain limit value, the second bypass line is interrupted again. Then dialysis fluid at the correct temperature and/or conductivity reaches the dialyzer.
When the second bypass valve is opened, the flow path through the first chamber of the dialyzer is advantageously interrupted. The flow path is interrupted with a shutoff device arranged upstream from the dialyzer in the dialysis fluid inlet line. A second shutoff device is preferably provided downstream from the dialyzer in the dialysis fluid outlet line.
The conductivity and/or temperature of the dialysis fluid can be determined with a first measurement device arranged downstream of the sterile filter in the direction of flow away from the dialyzer or a second measurement device arranged in the dialysis fluid outlet line downstream from the second bypass line when the dialysis fluid flows through the second bypass line to the drain.
To ensure that only dialysis fluid with a certain conductivity and/or temperature will reach the dialyzer, the temperature and/or conductivity of the dialysis fluid is advantageously monitored with a measurement device arranged in the dialysis fluid inlet line upstream from the sterile filter. If the deviation in the measured temperature and/or conductivity from a preset temperature and/or conductivity value exceeds a certain limit, the first chamber of the sterile filter is switched to continuous flow through the first bypass line, and the part of the dialysis fluid path leading to the dialyzer is interrupted. The conductivity and/or temperature of the dialysis fluid is then advantageously monitored with the measurement device arranged in the dialysis fluid inlet line upstream from the sterile filter or with a measurement device advantageously arranged in the dialysis fluid outlet line downstream from the first bypass line. If the deviation in the temperature and/or conductivity from a preset temperature and/or conductivity value falls outside a certain limit, the bypass line is interrupted so that dialysis fluid again flows through the sterile filter. This ensures that only dialysis fluid at a certain conductivity and/or temperature will reach the dialyzer.
Maintaining accurate temperature and/or conductivity values in the dialysis fluid is also important in particular when substituate obtained online from the dialysis fluid is supplied to the patient.